Electric motor driven tool for orthopedic impacting

ABSTRACT

An orthopedic impacting tool including a motor, an energy storage chamber, a striker, and an anvil. The motor stores energy in the energy storage chamber and then releases it, causing the striker to apply a controlled force on an adapter to create a precise impact for use in a surgical setting. The tool may further comprise a combination anvil and adapter. Alternatively, the tool may comprise a gas spring assembly system for generating an impact force. The tool further allows forward or backward impacting for expanding the size or volume of the opening or for facilitating removal of a broach, implant, or other surgical implement from the opening. An energy adjustment control of the tool allows a surgeon to increase or decrease the impact energy. A light source and hand grips improve ease of operation of the tool.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of 35 USC §119 to pendingU.S. Provisional Patent Application No. 62/101,416, filed on Jan. 9,2015, the entire disclosure of which is incorporated by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates to electric tools for impacting insurgical applications such as orthopedic procedures, and, moreparticularly, to an electric motor driven tool for surgical impactingthat is capable of providing controlled impacts to a broach or other endeffector.

BACKGROUND

In the field of orthopedics, prosthetic devices, such as artificialjoints, are often implanted or seated in a patient's bone cavity. Thecavity is typically formed during surgery before the prosthesis isseated or implanted, for example, a physician may remove and or compactexisting bone to form the cavity. A prosthesis usually includes a stemor other protrusion that is inserted into the cavity.

To create the cavity, a physician may use a broach conforming to theshape of the stem of the prosthesis. Solutions known in the art includeproviding a handle with the broach for manual hammering by the physicianduring surgery to impel the broach into the implant area. Unfortunately,this approach is imprecise, leading to unnecessary mechanical stress onthe bone and highly unpredictable depending upon the skill of aparticular physician. Historically, this brute force approach will inmany cases result in inaccuracies in the location and configuration ofthe cavity. Additionally, the surgeon is required to expend an unusualamount of physical force and energy to hammer the broach and tomanipulate the bones and prosthesis. Most importantly, this approachcarries with it the risk that the physician will cause unnecessaryfurther trauma to the surgical area and damage otherwise healthy tissue,bone structure and the like.

Another technique for creating the prosthetic cavity is to drive thebroach pneumatically, that is, by compressed air. This approach isdisadvantageous in that it prevents portability of an impacting tool,for instance, because of the presence of a tethering air-line, air beingexhausted from a tool into the sterile operating field and fatigue ofthe physician operating the tool. This approach, as exemplified in U.S.Pat. No. 5,057,112, does not allow for precise control of the impactforce or frequency and instead functions very much like a jackhammerwhen actuated. Again, this lack of any measure of precise control makesaccurate broaching of the cavity more difficult, and leads tounnecessary patient complications and trauma.

A third technique relies on computer-controlled robotic arms forcreating the cavity. While this approach overcomes the fatiguing andaccuracy issues, it suffers from having a very high capital cost andadditionally removes the tactile feedback that a surgeon can get from amanual approach.

A fourth technique relies on the author's own, previous work to use alinear compressor to compress air on a single stroke basis and then,after a sufficient pressure is created, to release the air through avalve and onto a striker. This then forces the striker to travel down aguide tube and impact an anvil, which holds the broach and or othersurgical tool. This invention works quite well, but, in the process oftesting it, does not allow for a simple method to reverse the broachshould it become stuck in the soft tissue. Further, the pressure of theair results in large forces in the gear train and linear motionconverter components, which large forces lead to premature wear oncomponents.

Consequently, there exists a need for an impacting tool that overcomesthe various disadvantages of existing systems and previous proprietarysolutions of the inventor

SUMMARY

In view of the foregoing disadvantages, an electric motor-drivenorthopedic impacting tool is provided for orthopedic impacting in hips,knees, shoulders and the like. The tool is capable of holding a broach,chisel, or other end effector and gently tapping the broach, chisel orother end effector into the cavity with controlled percussive impacts,resulting in a better fit for the prosthesis or the implant. Further,the control afforded by such an electrically manipulated broach, chisel,or other end effector allows adjustment of the impact settings accordingto a particular bone type or other profile of a patient. The tooladditionally enables proper seating or removal of the prosthesis or theimplant into or out of an implant cavity and advantageously augments theexisting surgeon's skill in guiding the instrument.

In an exemplary embodiment, an electric motor-driven orthopedicimpacting tool comprises a local power source (such as a battery or fuelcell), a motor, a controller, a housing, a module for converting therotary motion of the motor to a linear motion (hereafter referred to asa linear motion converter), at least one reducing gear, a striker, adetent and an energy storage mechanism, which energy storage mechanismcan include either compressed air or a vacuum. The tool may furtherinclude an LED, a handle portion with at least one handgrip for thecomfortable gripping of the tool, an adapter configured to accept asurgical tool, a battery and at least one sensor. At least some of thevarious components are preferably contained within the housing. The toolis capable of applying cyclic impact forces on a broach, chisel, orother end effector, or an implant and of finely tuning an impact forceto a plurality of levels. As no connections to the device are required,the device is portable.

In another embodiment, the orthopedic impacting tool may comprise a gasspring assembly system for generating an impact force applied to abroach, chisel, or other end effector. The gas spring assembly system isactuatable by a motor and gearbox in combination with a cam, whichreleases a gas spring piston that, in turn, accelerates a launching massfor generating the impact force. As an example, after a sufficientdisplacement of the gas spring piston, in which stored potential energyof the gas spring is increased, the gas spring piston is released fromthe cam. Upon release of the gas spring piston, the launched mass isaccelerated in the forward direction with the gas spring piston until itcomes into operative contact with the point of impact, the anvil oranother impact surface. In an embodiment, the launched mass separatesfrom the gas spring piston prior to its point of impact. There are atleast two different impacting surfaces for the launched mass, a forwardimpact surface and a different surface for rearward impact. The ratio ofthe gas spring piston mass to the total moving mass, i.e., the gasspring piston in combination with the launched mass, is less than 50%,which facilitates a more efficient transfer of energy to the launchedmass for imparting an effective impact. Further, the compression ratioof the gas spring is less than about 50%, which reduces thermal lossesfrom the heat of compression. After the launched mass impacts the impactsurface or point of contact, the cam re-cocks the gas spring piston forthe next cycle, if a trigger is maintained.

In a further embodiment, the handle may be repositionable or foldableback to the tool to present an inline tool wherein the surgeon pushes orpulls on the tool co-linearly with the direction of the broach. This hasthe advantage of limiting the amount of torque the surgeon may put onthe tool while it is in operation. In a further refinement of the handgrip, there may be an additional hand grip for guiding the surgicalinstrument and providing increased stability during the impactingoperation.

In a further embodiment, the broach, chisel or other end effector can berotated to a number of positions while still maintaining axialalignment. This facilitates the use of the broach for various anatomicalpresentations during surgery.

In a further embodiment, the energy storage mechanism comprises achamber, which is under at least a partial vacuum during a portion of animpact cycle.

In a further embodiment the linear motion converter uses one of a slidercrank, linkage mechanism, cam, screw, rack and pinion, friction drive orbelt and pulley.

In an embodiment, the linear motion converter and rotary motor may bereplaced by a linear motor, solenoid or voice coil motor.

In a further embodiment, the tool further comprises a control element,which includes an energy adjustment element, and which energy adjustmentelement may control the impact force of the tool and reduce or avoiddamage caused by uncontrolled impacts. The energy may be regulatedelectronically or mechanically. Furthermore, the energy adjustmentelement may be analog or have fixed settings. This control elementallows for the precise control of the broach machining operation.

In an embodiment, an anvil of the tool includes at least one of twopoints of impact and a guide that constrains the striker to move in asubstantially axial direction. In operation, the movement of the strikeralong the guide continues in the forward direction. A reversingmechanism can be used to change the point of impact of the striker andthe resulting force on the surgical tool. Use of such a reversingmechanism results in either a forward or a rearward force being exertedon the anvil and/or the broach or other surgical attachment. As used inthis context, “forward direction” connotes movement of the strikertoward a broach, chisel or patient, and “rearward direction” connotesmovement of the striker away from the broach, chisel or patient. Theselectivity of either bidirectional or unidirectional impacting providesflexibility to a surgeon in either cutting or compressing materialwithin the implant cavity in that the choice of material removal ormaterial compaction is often a critical decision in a surgicalprocedure. Furthermore, it was discovered in the use of the author'sown, previous work that the tool would often get stuck during theprocedure and that the method of reversal in that tool was insufficientto dislodge the surgical implement. The present embodiments disclosedherein overcome this drawback. In an embodiment the impact points tocommunicate either a forward or rearward force are at least two separateand distinct points.

In an embodiment the anvil and the adapter comprise a single element, orone may be integral to the other.

In an embodiment the tool is further capable of regulating the frequencyof the striker's impacting movement. By regulating the frequency of thestriker, the tool may, for example, impart a greater total time-weightedpercussive impact, while maintaining the same impact magnitude. Thisallows for the surgeon to control the cutting speed of the broach orchisel. For example, the surgeon may choose cutting at a faster rate(higher frequency impacting) during the bulk of the broach or chiselmovement and then slow the cutting rate as the broach or chiselapproaches a desired depth. In typical impactors, as shown in U.S. Pat.No. 6,938,705, as used in demolition work, varying the speed varies theimpact force, making it impossible to maintain constant (defined as+/−20%) impact energy in variable speed operation.

In an embodiment the direction of impacting is controlled by the biasingforce placed by a user on the tool. For example, biasing the tool in theforward direction gives forward impacting and biasing the tool in therearward direction gives rear impacting.

In an embodiment the tool may have a lighting element to illuminate awork area and accurately position the broach, chisel, or other endeffector on a desired location on the prosthesis or the implant.

In an embodiment the tool may also include a feedback system that warnsthe user when a bending or off-line orientation beyond a certainmagnitude is detected at a broach, chisel, or other end effector orimplant interface.

In an embodiment the tool may also include a detent that retains thestriker and which may be activated by a mechanical or electricalcontroller such that the energy per impact from the tool to the surgicalend effector is increased. In an embodiment, the characteristics of thisdetent are such that within 30% of striker movement, the retention forceexerted by the detent on the striker is reduced by about 50%.

These together with other aspects of the present disclosure, along withthe various features of novelty that characterize the presentdisclosure, are pointed out with particularity in the claims annexedhereto and form a part of the present disclosure. For a betterunderstanding of the present disclosure, its operating advantages, andthe specific non-limiting objects attained by its uses, reference shouldbe made to the accompanying drawings and detailed description in whichthere are illustrated and described exemplary embodiments of the presentdisclosure.

DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The advantages and features of the present invention will become betterunderstood with reference to the following detailed description andclaims taken in conjunction with the accompanying drawings, wherein likeelements are identified with like symbols, and in which:

FIG. 1 shows a perspective view of an orthopedic impacting tool inaccordance with an exemplary embodiment of the present disclosure;

FIG. 2 shows an exemplary position of a piston of the tool of FIG. 1during vacuum operation;

FIG. 3 shows a striker of the tool of FIG. 1 moving towards impactingthe anvil in a forward direction;

FIG. 4 shows the striker of the tool of FIG. 1 moving such that theanvil will be impacted in a reverse direction;

FIG. 5 shows a piston of the tool of FIG. 1 moving back towards a firstposition and resetting the striker;

FIG. 6 shows a further exemplary embodiment of a tool in which acompression chamber is used to create an impacting force;

FIG. 7 shows an exemplary embodiment of a tool in which a valve is usedto adjust the energy of the impact of the striker;

FIG. 8 shows an exemplary embodiment of a tool in which the strikerimparts a surface imparting a rearward force on the anvil;

FIG. 9 shows an exemplary embodiment of a tool in which the strikerimparts a forward acting force on the anvil;

FIG. 10 is a chart comparing the force vs. time curve between a sharpimpact and a modified impact using a compliance mechanism in accordancewith an exemplary embodiment of the present disclosure;

FIG. 11 shows a perspective view of an orthopedic impacting tool inaccordance with a further embodiment of the present disclosure in whicha gas spring assembly system is used for generating an impact force;

FIG. 12 shows a perspective view of the gas spring assembly system inwhich a cam is used for actuating a gas spring;

FIG. 13 shows an exemplary embodiment of the tool in which the cam ofthe gas spring assembly system has released the gas spring;

FIG. 14 shows an exemplary embodiment of the tool in which after the gasspring has been released, a launched mass is accelerated towards a pointof impact in a forward direction; and

FIG. 15 is an exemplary flow chart illustrating a cyclic operation of anorthopedic impacting tool in accordance with an exemplary embodiment ofthe present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

The preferred embodiments described herein detail for illustrativepurposes are subject to many variations. It is understood that variousomissions and substitutions of equivalents are contemplated ascircumstances may suggest or render expedient, but are intended to coverthe application or implementation without departing from the spirit orscope of the present disclosure.

The present disclosure provides an electric motor-driven orthopedicimpacting tool with controlled percussive impacts. The tool includes thecapability to perform single and multiple impacts as well as impactingof variable and varying directions, forces and frequencies. In anembodiment the impact force is adjustable. In another embodiment adetent may be provided, which detent facilitates the generation of ahigher energy impact. In yet another embodiment the impact istransferred to a broach, chisel, or other end effector connected to thetool.

The tool may further include a housing. The housing may securely coverand hold at least one component of the tool and is formed of a materialsuitable for surgical applications. In an embodiment, the housingcontains a motor, at least one reducing gear, a linear motion converter,a gas chamber, a striker, a force adjuster, a control circuit or module,an anvil, a forward impact surface and a different surface for rearwardimpact.

The tool further may include a handle portion with an optional hand gripfor comfortable and secure holding of the tool while in use, and anadapter, a battery, a positional sensor, a directional sensor, and atorsional sensor. The tool may further comprise a lighting element suchas an LED to provide light in the work area in which a surgeon employsthe tool. The anvil may be coupled to a broach, chisel or other endeffector known in the art through the use of an interfacing adapter,which adapter may have a quick connect mechanism to facilitate rapidchange of different broaching sizes. The anvil may further include alocking rotational feature to allow the broach to be presented to andconfigured at different anatomical configurations without changing theorientation of the tool in the surgeon's hands.

Referring now generally to FIGS. 1 through 5, in an exemplaryembodiment, the linear motion converter 12 comprises a slider crankmechanism. The slider crank is operatively coupled, directly orindirectly, to the motor 8 and reducing gears 7. The tool furthercomprises a vacuum chamber 23 that accepts a piston 24 which may beactuated by the linear motion converter 12. It will be apparent that thepiston 24 may be actuated in more than one direction. The vacuum iscreated in the vacuum chamber 23 by the movement of piston 24 away fromstriker 25. The vacuum created in the vacuum chamber 23 is defined as apressure of less than about 9 psia for at least a portion of theoperational cycle.

In an embodiment, the motor 8 causes the linear motion converter 12 tomove, which pulls a vacuum on the face of the striker 25 and creates atleast a partial vacuum in the vacuum chamber 23, as is shown moreparticularly in FIG. 2. The piston 24 continues to move increasing thesize of the vacuum chamber 23 until it hits a forward portion of thestriker 25 (i.e., a portion of the strike that is proximate to the endeffector or patient), which dislodges the striker 25 from its detent 10(for embodiments employing a detent) and allows it to rapidly acceleratetowards the end of the tool that is proximate to the end effector orpatient. In an embodiment, the detent may be mechanical, electrical, ora combination thereof, with the preferred detent shown in the figures asa magnet or electromagnet. A characteristic of the detent 10 is thatonce the detent 10 is released or overcome, the retention force of thedetent 10 on the striker 25 reduces by at least about 50% within thefirst 30% movement of the striker 25. The impact of the striker 25 onthe anvil 14 communicates a force to the adapter 1 and the broach,chisel or other orthopedic instrument.

In an exemplary embodiment, the direction of the force on the anvil iscontrolled by the user's (such as a surgeon) manual force on the tooland a stroke limiter 13. It has been determined by the inventor that hisprevious designs may occasionally seize in a cavity and the impact ofthe striker in the aforementioned paragraph may be insufficient todislodge the tool. In this present embodiment, when the tool is beingpulled away from the cavity, the striker 25 will not impact the anvil14, but will impact an alternate surface and thereby communicate arearward force on the anvil 14. This impact surface is shown in anexemplary embodiment as actuation pin 27. Actuation pin 27 communicatesa force to lever arm 17, which communicates a rearward force on theanvil 14, and specifically on the anvil retract impact surface 26. Thisembodiment has the unexpected benefit of readily solving theaforementioned seizure problem, while retaining all the benefits of theexisting tool in terms of precision-controlled impacting. Thus, afurther advantage of this tool was discovered as it can be seen that thesurgeon can control the direction of the impacting by a bias that he orshe may place on the tool and, in so doing, can reduce the likelihood ofthe broach, chisel or other end effector from getting stuck in a patientor surgical cavity.

In a further embodiment, an electromagnet may be incorporated as thedetent 10 and released at an appropriate point in the operation cycle toallow the striker 25 to impact the anvil 14. Once the striker 25 hasbeen released from the detent 10, the air pressure on the rearward sideof the striker 25, propels it forward to impact the anvil 14 or otherstrike surface. The resultant force may be communicated through an endof the anvil 14 that is proximate to the anvil forward impact surface 16and, optionally, through the adapter 1 to which a broach, chisel, orother end effector for seating or removing an implant or prosthesis maybe attached.

The striker guide 11 may also have striker guide vent holes 20, whichallow the air in front of the striker 25 to escape, thus increasing theimpact force of the striker 25 on the anvil 14. The striker guide ventholes 20 may vent within the cavity of the tool body, thus creating aself-contained air cycle preventing air from escaping from the tool andallowing for better sealing of the tool. The inventor has determinedthat the position and the size of the striker guide vent holes 20 can bevaried to regulate the impact force. Further, the inventor determinedthat adding the striker guide vent holes 20 increases the impact forceof the striker 25 on the anvil 14.

In an embodiment, as the piston 24 continues through its stroke it movestowards the rear direction. This movement brings the piston 24 incontact with rear striker face 28 of striker 25 and moves it towards therear of the tool. This allows the detent 10 to lock or retain thestriker 25 in position for the next impact. The piston 24 completes itsrearward stroke and preferably activates a sensor 22 that signals themotor 8 to stop such that the piston 24 rests at or near bottom deadcenter of the vacuum chamber 23. The vacuum chamber 23 preferably has arelief or check valve 9 or other small opening, which, in an embodiment,is part of the piston 24. The valve 9 may also be located at otherpoints in the vacuum chamber 23 and allows for any air which may haveaccumulated in the vacuum chamber 23 to be purged out of the vacuumchamber 23 during each cycle. In a further embodiment this valve effectcould be accomplished with a cup seal instead of an O-ring seal. Thisensures that approximately atmospheric pressure is present in the vacuumchamber 23 at a starting point in the operational cycle, thus ensuringthat each impact utilizes the same amount of energy, as is important inorthopedic impacting for at least the reason that it assures of asubstantially consistent force and impact rate in multi-impactsituations. Thus, in one complete cycle, a forward or a rearwardimpacting force may be applied on the broach, chisel, or other endeffector, or on the implant or prosthesis.

FIG. 15 is an exemplary flow chart illustrating a cyclic operation of anorthopedic impacting tool according to an exemplary embodiment of thepresent disclosure. At the start of the cycle 1500, it is firstdetermined in step 1502 whether the orthopedic impacting tool is chargedand ready for use. If a voltage of a local power source, such as abattery, is less than a threshold minimum, then the battery is set tocharge in step 1504. If the voltage of the battery is greater than thethreshold minimum, then it is next determined in step 1506 whether ananvil and/or broach or other surgical attachment is correctly positionedrelative to a cavity of the patient's bone. If the anvil and/or thebroach or other surgical attachment is correctly positioned, theoperation moves on to step 1510; otherwise, the system waits until theposition is corrected in step 1508. In step 1510, it is determinedwhether an electric motor and gearbox combination is rotating. Once themotor starts to rotate, it is next determined in step 1512 whether a camsensor has been activated. If the sensor has been activated, then atrigger is pressed in step 1514, which results in a cam to “cock” a gasspring piston and ultimately generate an impact force. If the cam sensorhas not been activated, then the process returns to step 1510 to allowthe motor to continue rotating until the cam sensor has been activated.Next, if a trigger is maintained in step 1514, then the operation cyclesback to step 1510 where the motor continues to rotate, causing the camto “re-cock” the gas spring piston for the next cycle; otherwise, theoperation of the orthopedic impacting tool ceases at step 1516.

A controller 21 preferably operates with firmware implementing thecyclic operation described in FIG. 15, which results in the orthopedicimpacting tool being able to generate a repeatable, controllableimpacting force. The controller 21 can include, for example, intelligenthardware devices, e.g., any data processor, microcontroller or FPGAdevice, such as those made by Intel® Corporation (Santa Clara, Calfi.)or AMD® (Sunnyvale, Calif.). Other controller types could also beutilized, as recognized by those skilled in the art.

In a further embodiment, the motor 8 of the tool causes the linearmotion converter 12 to move the piston 24 until the piston 24 moves asufficient distance such that the forward portion of the piston impactsa portion of the striker and overcomes the detent 10 that retains thestriker in the rear position. Once the striker has been released fromthe detent 10, the vacuum in the vacuum chamber 23 exerts a force on thestriker, which accelerates the striker, causing the striker to slideaxially down a cavity internal to the tool housing and strike the anvilforward impact surface 16. In FIG. 3, the anvil forward impact surface16 causes a forward movement of the anvil 14 and/or tool holder, and, inFIG. 4, the anvil retract impact surface 26 causes a rearward movementof the anvil 14 and/or tool holder. The resultant force is communicatedthrough an end of the anvil 14 that is proximate to the anvil forwardimpact surface 16 and, optionally, through the adapter 1 to which abroach, chisel, or other end effector for seating or removing an implantor prosthesis may be attached.

In another exemplary embodiment, the impact force may be generated usinga compressed air chamber 5 in conjunction with a piston 6 and striker 4,as shown generally in FIGS. 6 through 9. In this embodiment, the motor 8of the tool causes the linear motion converter 12 to move the piston 6until sufficient pressure is built within the compressed air chamber 5that is disposed between the distal end of the piston 6 and theproximate end of the striker 4 to overcome a detent 10 that otherwiseretains the striker 4 in a rearward position and or the inertia andfrictional force that holds the striker 4 in that rearward position.Once this sufficient pressure is reached, an air passageway 19 is openedand the air pressure accelerates the striker 4, which striker 4 slidesaxially down a cavity and strikes the anvil 14. The air passageway 19has a cross sectional area of preferably less than 50% of the crosssectional area of the striker 4 so as to reduce the amount of retainingforce required from detent 10. The resultant force is communicatedthrough the end of the anvil 14 that is proximate to the anvil forwardimpact surface 16 and, optionally, through the adapter 1 to which abroach, chisel, or other device for seating or removing an implant orprosthesis may be attached.

As the piston 6 continues through its stroke, it moves towards the reardirection, pulling a slight vacuum in compressed air chamber 5. Thisvacuum may be communicated through an air passageway 19 to the back sideof the striker 4, creating a returning force on the striker 4, whichreturning force causes the striker 4 to move in a rear direction, i.e.,a direction away from the point of impact of the striker 4 on the anvilforward impact surface 16. In the event that an adapter 1 is attached tothe anvil 14, a force may be communicated through the adapter 1 to whichthe broach, chisel, or other end effector for seating or removing animplant or prosthesis is attached.

In another exemplary embodiment, the impact force may be generated usinga gas spring assembly system, such as an air spring assembly system, asillustrated, for example, in FIG. 11. FIG. 11 shows a perspective viewof an orthopedic impacting tool in accordance with an embodiment of thepresent disclosure in which a motor and gearbox 8 of the gas springassembly system, in combination with a cam 30, actuates a gas springpiston 32 and/or a launched mass 34, in order to ultimately generate animpact force. The cam 30 is shown in tear drop shape, but the designcontemplates that any shape may be used which provides a quick releaseof the gas spring. Alternative ways for actuating and quickly releasingthe gas spring include, but are not limited to, using an interruptedrack and pinion or a climbing mechanism. The gas spring assembly systemfurther includes, among other components, a roller follower 36, reducinggears 7 and an anvil 14. The gas spring piston 32 includes a gas chamber40 which operates under pressure in a range of about 300 to 3000 psi,for example.

FIG. 12 is a perspective view of the gas spring assembly system in whichthe cam 30 used for actuating the gas spring piston 32 has the gasspring “cocked” in the operative position, ready for release. In the“cocking phase” the gas spring piston 32 in combination with thelaunched mass 34 contacts and is pushed by the roller follower 36, whichis driven by the cam 30 in a first direction, as shown by arrow 42. Asthe cam 30 continues to rotate in the first direction (viewed asclockwise for tautological purposes), the gas spring piston 32 incombination with the launched mass 34 is released off of the cam 30. Inparticular, after a sufficient displacement of the gas spring piston 32within the gas chamber 40, and after the cam 30 releases the gas springpiston 32 and/or the launched mass 34 combination, the gas spring piston32 moves in a forward direction, i.e., a direction toward the point ofimpact, and, at the same time, accelerates the launched mass 34, whichis in contact with the face of the gas spring piston 32. The launchedmass 34 may be constructed from a suitable material such as steel or anyother material having similar properties lending itself to repeatedimpacting.

FIGS. 13 and 14 show an exemplary embodiment of the orthopedic impactingtool in which the cam 30 of the gas spring assembly system has beenrotated in the first direction 42 and the gas spring piston 32 has beenreleased off of the cam 30. Upon release of the gas spring piston 32,the launched mass 34 is accelerated in the forward direction with thegas spring piston 32 until it comes into operative contact with thepoint of impact, the anvil 14 or another impact surface. As the gasspring piston 32 moves in the forward direction, a gas spring bumper 44functions as a stopper to prevent a flange 46 of the gas spring piston32 from impacting the cylinder of the gas spring piston 32. The bumper44 absorbs the impact of the gas spring piston 32 as it comes to the endof the stroke and launches the mass 34. Such bumper 44 prevents damageto the gas spring piston 32 during repeated operation. During at least aportion of the impact, and preferably prior to the point of impact, thelaunched mass 34 separates from the face of the gas spring piston 32.The cam 30 then re-cocks the gas spring piston 32 for the next cycle, ifa trigger is maintained.

As discussed above, there are at least two different impacting surfaces,a forward impact surface and a different surface for rearward impact.FIG. 14 shows the lever arm 17, which communicates a rearward force onthe anvil 14, and specifically on a different surface for rearwardimpact. Such has the unexpected benefit of easily dislodging tools andinstruments that have become stuck in a surgical cavity. With specificreference to FIGS. 6, 8 and 9, for example, when the orthopedicimpacting tool is being pulled away from the cavity of a bone of thepatient, for example, the striker 4 will not impact the anvil 14, butmay instead impact an alternate surface and thereby communicate arearward force on the anvil 14. This impact surface is shown in anexemplary embodiment as actuation pin 27. Actuation pin 27 communicatesa force to lever arm 17, which communicates a rearward force on theanvil 14, and specifically on the anvil retract impact surface 26.

The ratio of the gas spring piston 32 mass to the total moving mass,i.e., the gas spring piston 32 in combination with the launched mass 34,is less than about 50%, which facilitates a more efficient energytransfer to the launched mass 34 for imparting an effective impact onthe impact surface. Advantageously, the gas spring assembly system doesnot need or use a detent or a magnet for generating the higher energyimpact. Further, the compression ratio of the gas spring is less than50%, which reduces thermal heat generated during the compression of thegas. Accordingly, the gas spring assembly system is more compact,efficient, weighs less and has less total and moving parts as comparedto the earlier described impact generating systems.

The tool may further facilitate controlled continuous impacting, whichimpacting is dependent on a position of a start switch (which startswitch may be operatively coupled to the power source or motor, forexample). For such continuous impacting, after the start switch isactivated, and depending on the position of the start switch, the toolmay go through complete cycles at a rate proportional to the position ofthe start switch, for example. Thus, with either single impact orcontinuous impacting operational modes, the creation or shaping of thesurgical area is easily controlled by the surgeon.

A sensor 22 coupled operatively to the controller 21 may be provided toassist in regulating a preferred cyclic operation of the linear motionconverter 12. For example, the sensor 22 may communicate at least oneposition to the controller 21, allowing the linear motion converter 12to stop at or near a position in which at least about 75% of a fullpower stroke is available for the next cycle. This position is referredto as a rest position. This has been found to be advantageous overexisting tools in that it allows the user to ensure that the toolimpacts with the same amount of energy per cycle. Without this level ofcontrol, the repeatability of single cycle impacting is limited,reducing the confidence the surgeon has in the tool.

The tool is further capable of tuning the amount of impact energy percycle by way of, for example, an energy control element 18. Bycontrolling the impact energy the tool can avoid damage caused byuncontrolled impacts or impacts of excessive energy. For example, asurgeon may reduce the impact setting in the case of an elderly patentwith osteoporosis, or may increase the impact setting for more resilientor intact athletic bone structures.

In an embodiment, the energy control element 18 preferably comprises aselectable release setting on the detent 10 that holds the striker 25.It will be apparent that the striker 25 will impact the anvil 14 withgreater energy in the case where the pressure needed to dislodge thestriker 25 from the detent 10 is increased. In another embodiment, thedetent 10 may comprise an electrically controlled element. Theelectrically controlled element can be released at different points inthe cycle, thus limiting the size of the vacuum chamber 23, which isacting on the striker 25. In an embodiment, the electrically controlledelement is an electromagnet.

In another embodiment, the vacuum chamber 23 or compressed air chamber 5may include an energy control element 18, which takes the form of anadjustable leak, such as an adjustable valve. The leakage reduces theamount of energy accelerating the striker 4 or 25, thus reducing theimpact energy on the anvil 14. In the case of the adjustable leak,adjusting the leak to maximum may give the lowest impact energy from thestriker 4 or 25, and adjusting to shut the leak off (zero leak) may givethe highest impact energy from the striker 4 or 25.

The tool may further comprise a compliance element inserted between thestriker 4 or 25 and the surgical end effector, which purpose is tospread the impact force out over a longer time period, thus achievingthe same total energy per impact, but at a reduced force. This can beseen clearly as a result of two load cell tests on the instrument asshown in FIG. 10. This type of compliance element can limit the peakforce during impact to preclude such peaks from causing fractures in thepatient's bone. In a further embodiment, this compliance element may beadjustable and in a still further embodiment the compliance element maybe inserted between striker 4 or 25 and the anvil 14 or surgical tool.In this manner and otherwise, the tool facilitates consistent axialbroaching and implant seating. Preferably, the compliance Elementincreases the time of impact from the striker to at least 4 millisecondsand preferable 10 milliseconds. This contrasts to impacting in which avery high force is generated due to the comparatively high strengths ofthe striker 4 or 25 and the anvil 14 (both steel, for example).Preferably, the compliance Element comprises a resilient material suchas urethane, rubber or other elastic material that recovers well fromimpact and imparts minimal damping on the total energy.

In a further embodiment, the adapter 1 may comprise a linkagearrangement or other adjustment mechanisms known in the art such thatthe position of the broach, chisel or other end effector can be modifiedwithout requiring the surgeon to rotate the tool. In an embodiment, theadapter 1 may receive a broach for anterior or posterior jointreplacement through either an offset mechanism or by a rotational orpivotal coupling between the tool and the patient. The adapter 1 maythereby maintain the broach or surgical end effector in an orientationthat is parallel or co-linear to the body of the tool and the striker25. The adapter 1 may also comprise clamps, a vice, or any otherfastener that may securely hold the broach, chisel, or other endeffector during operation of the tool.

In use, a surgeon firmly holds the tool by the handle grip or grips andutilizes light emitted by the LED to illuminate a work area andaccurately position a broach, chisel or other end effector that has beenattached to the tool on a desired location on the prosthesis or implant.The reciprocating movement imparted by the tool upon the broach, chiselor other end effector allows for shaping a cavity and for seating orremoval of a prosthesis.

The tool disclosed herein provides various advantages over the priorart. It facilitates controlled impacting at a surgical site, whichminimizes unnecessary damage to a patient's body and which allowsprecise shaping of an implant or prosthesis seat. The tool also allowsthe surgeon to modulate the direction, force and frequency of impacts,which improves the surgeon's ability to manipulate the tool. The forceand compliance control adjustments of the impact settings allow asurgeon to set the force of impact according to a particular bone typeor other profile of a patient. The improved efficiency and reducedlinear motion converter loads allow use of smaller batteries and lowercost components. The tool thereby enables proper seating or removal ofthe prosthesis or implant into or out of an implant cavity.

The foregoing descriptions of specific embodiments of the presentdisclosure have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit thepresent disclosure to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The exemplary embodiment was chosen and described in order tobest explain the principles of the present disclosure and its practicalapplication, to thereby enable others skilled in the art to best utilizethe disclosure and various embodiments with various modifications as aresuited to the particular use contemplated.

What is claimed is:
 1. A surgical impactor for striking an object with arepeatable, controlled contacting force to impel the operation of asurgical implement in opposing directions, the impactor comprising: adrive mechanism with a gas spring assembly; a control circuit to controlstorage and release of energy output from the drive to an energy storagemechanism to produce the repeatable, controlled contacting force; anadapter configured to receive a surgical implement to interface theobject; and a moving body operable to contact at least two distinctimpact surfaces based upon the repeatable, controllable contacting forcedelivered thereto to provide the repeatable controlled contacting forceto the adapter, the provision of the repeatable, controllable contactingforce to a first impact surface impels the adapter in a first direction,the provision of the repeatable controllable contacting force to asecond impact surface impels the adapter in a direction opposite thefirst direction.
 2. The impactor of claim 1, wherein the selection ofthe at least two impact surfaces is based upon a user bias force appliedto the impactor.
 3. The impactor of claim 2, wherein the user bias forcein a direction of the object causes the moving body to contact the firstimpact surface.
 4. The impactor of claim 2, wherein the user bias forcein a direction away from the object causes the moving body to contactthe second impact surface.
 5. The impactor of claim 1, wherein the gasspring assembly includes a gas spring, a gas spring piston, a cam, amotor and a gearbox.
 6. The impactor of claim 5, wherein a ratio of agas piston mass to a total moving mass of the gas spring piston and themoving body is less than 50%.
 7. The impactor of claim 5, wherein acompression ratio of the gas spring is less than 50%.
 8. The impactor ofclaim 5, wherein the cam is used for displacing the gas spring piston.9. The impactor of claim 5, wherein the gas spring piston includes a gaschamber operating under a pressure in a range of 300 to 3000 psi. 10.The impactor of claim 1, wherein the moving body includes the gas springpiston and a moving mass.
 11. The impactor of claim 1, wherein themoving body includes a moving mass.
 12. The impactor of claim 11,wherein the moving mass is composed of steel.
 13. The impactor of claim1, further comprising: an energy adjustment mechanism to adjust impactenergy the moving body delivers to the adapter in accordance with apatient profile.
 14. The impactor of claim 1, wherein the adapter isconfigured to releasably connect to the surgical implement.
 15. Theimpactor of claim 1, wherein the moving body is operably linked to theadapter by an anvil having the at least two impact surfaces.
 16. Theimpactor of claim 15, wherein the adapter is impelled in a directionopposite the first direction by means of a lever arm which applies arearward force on the anvil.
 17. The impactor of claim 5, wherein thecam engages the gas spring piston prior to the moving body contactingthe at least two distinct impact surfaces and releases the gas springpiston from the cam to impel the moving body to contact the at least twodistinct impact surfaces.
 18. The impactor of claim 10, wherein themoving mass is attached to a face of the gas spring piston prior tocontacting the at least two distinct impact surfaces.
 19. The impactorof claim 18, wherein the moving mass separates from the face of the gasspring piston during at least a portion of the contact with the at leasttwo distinct impact surfaces.
 20. A surgical impactor for striking anobject with a repeatable, controlled contacting force to impel theoperation of a surgical implement in opposing directions, the impactorcomprising: means for driving the impactor with a gas spring assembly,the gas spring assembly including a gas spring piston; a control circuitto control storage and release of energy, of the means for driving, toan energy storage device to produce the repeatable, controlledcontacting force; an implement mount to receive a surgical implement;and a moving body operable to contact at least two distinct impactsurfaces based upon the repeatable, controllable contacting forcedelivered thereto to provide the repeatable controlled contacting forceto the implement mount, the provision of the repeatable, controllablecontacting force to a first impact surface impels the implement mount ina first direction, the provision of the repeatable controllablecontacting force to a second impact surface impels the implement mountin a direction opposite the first direction.